1. Field of the Invention
This invention relates to an improved unitized wheel hub and bearing assembly for mounting on the ends of vehicle axles. More particularly, the improved assembly includes a pair of bearings, a bearing spacer, at least one seal and a wheel hub. By means of the assembly, the various elements may be pre-adjusted for controlling the bearing settings and, when two seals are used, may be prelubricated. Vanes are provided in the hub assembly to redirect lubricant motion from tangential to axial, as well as splitting the axial flow from unidirectional to bi-directional so as to improve lubricant distribution to the bearings to insure adequate cooling to extend their useful bearing life in the hub.
2. Description of Prior Art
In wheeled vehicles of all types, it is necessary to provide bearings for axles so that associated wheel hubs may rotate freely on the end of a relatively stationary axle. Such bearings must be lubricated and seals are required to retain the lubricating medium whether it be grease or oil. Frequently, wear sleeves are employed to prevent undue wear of the axle by the seals. Sometimes, such wear sleeves have been separate elements and sometimes they have been an integral part of a unitized seal.
Until quite recently, such bearing, seal and wheel hub means have been assembled piece by piece. The bearing races have been fitted to designated axle portions and corresponding portions of the associated wheel hub. The bearing elements are usually spaced as far apart axially as possible with a tapered axle portion between these elements. The assembly also includes one or two seals, depending upon the particular design. These wheel hub assemblies have typically provided long lasting performance when assembled properly. However, such an assembly process requires skilled personnel and proper equipment to achieve proper installation and operation. If repair or replacement of any part becomes necessary, correct positioning and adjustment of all elements becomes even more of a challenge and damaged parts are a quite likely result. Typical prior art assemblies are illustrated in U.S. Pat. No. 4,552,367 assigned to Garlock Inc. and U.S. Pat. No. 4,037,849 assigned to The Mechanex Corp.
A non-unitized wheel hub assembly requires the components to be assembled and installed on site by a mechanic working on an axle spindle. The nature of the assembling process, and the generally horizontal orientation of the spindle during assembly, makes it difficult to fill the assembly with a liquid such as oil and the non-unitized wheel hub assembly must be lubricated with packing grease or oil filled after installation. Therefore, there was a need for a unitized wheel hub assembly which allows the assembly to be pre-filled with oil to achieve superior lubrication characteristics in contrast to the non-unitized assemblies.
More recently, some efforts have been made to develop assemblies which permit more of the various elements to be pre-assembled and adjusted, thus resulting in less dependence on the skills of the field mechanic. One such attempt has been the SAF Euro-axle developed by the Otto Sauer Achsenfabric of Keilber, Germany. These units accomplish much in terms of allowing factory assembly and adjustments of sealed bearing units and avoidance of so much dependence on the skills of the field mechanic. However, these units are not constructed to allow prefilling with oil which is a preferred bearing lubricant as compared to grease. More significantly, a special axle is included in the assembly and the pre-assembled units cannot be adapted to the millions of existing axles presently in service.
Another recent effort at development of pre-assembled and pre-adjusted sealing bearing units has been made by SKF Sweden. However, as with SAF units described previously, the SKF units are not adapted to prefilling with oil lubrication and they are not adaptable to the millions of existing axis. Furthermore, since the bearing units are more closely located relative to one another, there can be a tendency toward lessened wheel stability in operation.
One recent effort at development of pre-assembled and pre-adjusted sealing bearing units which are prefilled with oil lubrication is illustrated in U.S. Pat. No. 5,328,275 assigned to Stemco Inc., the assignee of the present invention. These units also provide the advantage of being adaptable to the millions of existing axles. However, these units are installed onto the axle and held in axially proper position by the tightening of a spindle nut onto the axle spindle. The clamp load exerted from the tightening of the spindle nut is transmitted through a mounting sleeve to the spindle shoulder, wherein the degree to which the spindle nut is tightened should be within predetermined tolerances. However, the amount of clamp load exerted could undesirably vary from the desired tolerance range if the end user fails to comply. The thickness of the mounting sleeve wall is relatively thin as compared to the bearing inner races, and the tensile stresses resulting from the clamp load can cause damage to the mounting sleeve if the clamp load exceeds the design limits on the sleeve.
In U.S. patent application Ser. No. 08/604,196 filed on or about Apr. 18, 1996, now abandoned, and assigned to Stemco, Inc. also the assignee of the present invention, there is disclosed a unitized wheel hub and bearing assembly in which the bearing setting can be predetermined precisely by a spacer installed as part of the manufacturing process so that there is no variation in the bearing between different users installing the assembly, wherein the assembly can also be pre-filled with a lubricant. However, means must be provided to adequately direct oil to lubricate and cool the spaced and fixed bearings to prolong their useful life. This invention addresses this problem.